Adsorption characteristics of cationic surfactants on titanium dioxide with quaternary ammonium groups and their adsolubilization

Adsorption of cationic surfactants on titanium dioxide with quaternary ammonium groups (XNm, where m is the carbon number of the alkyl chain, 4-16) was investigated by measuring the amount of adsorbed surfactants, zeta potential, and dispersion stability. The cationic surfactants used were dodecyltrimethylammonium chloride (DTAC) and 1,2-bis(dodecyltrimethyl ammonio) ethane dichloride (2RenQCl). The amount of surfactants adsorbed increased with increasing chain length of XNm, accompanying a gradual increase of zeta potential. The dispersion stability of XNm was very high in a whole surfactant concentration region except that of untreated titanium dioxide. The electron spin resonance measurements using a spin probe methyl 12-doxylstearate show that the order parameters are very similar for XN4-12, but the order parameter for XN16 is higher than that for XN4-12. Adsolubilization of 2-naphthol on XNm by adsorption of surfactants was also carried out: the amount of 2-naphthol adsolubilized increased with increasing surfactant concentration where the amount adsolubilized increased with increasing chain length of XNm. Further, the adsorption of 2RenQCl enhanced the amount adsolubilized greater than by the adsorption of DTAC. (C) 1998 Academic Press.